1. Field of the Invention
This invention relate to a process for the optical resolution of (.+-.)-cis or (.+-.)-trans-permethric acid.
2. Description of the Prior Art
(.+-.)-Cis or (.+-.)-trans-permethric acid is a carboxylic acid, whose side chain substituent may be modified, and is used; as one ingredient of the esters called pyrethroid. Pyrethroid is an insecticidal component of pyrethrum. The (.+-.)-cis or (.+-.)-trans-permethric acid prepared by chemical synthesis is generally obtained in the form of optically inactive racemates; namely (.+-.)-carboxylic acids. (-)-Cis or (-)-trans-permethric acid contained in the (.+-.)-cis or (.+-.)-trans-permethric acid is far poorer in insecticidal activity than (+)-cis or (+)-trans-permethric acid. Accordingly, there is a demand of the development of a technique in which (.+-.)-cis or (.+-.)-trans-permethric acid is optically resolved in an efficient manner to obtain highly pure (+)-cis or (+)-trans-permethric acid.
Several processes of obtaining an optically active product of cis-permethric acid are known including processes of using, on (.+-.)-cis-permethric acid, resolving agents such as optically active N-benzyl-2-aminobutanol (U.S. Pat. No. 4,599,444), N-(2,2,2-trichloro-1-formamidoethyl)piperazine (U.S. Pat. No. 4,508,919), and 1-phenyl-2-(p-tolyl)ethylamine (U.S. Pat. No. 4,327,038). Also, there are known processes in which the acid is introduced into various derivatives and then resolved. However, the resolving agents used in these processes are relatively expensive and the yield of the optically active cis-permethric acid obtained by the resolution is not high, thus leading to the problem that the optically active cispermethric acid is expensive.
For obtaining an optically active product of transpermethric acid, there have been hitherto proposed a process in which optically active .beta.'-dimethylamino-.alpha.,.alpha.-dimethyl-.beta.-phenethyl alcohol is used with (.+-.)-transpermethric acid (Japanese Patent Publication No. 8815/81) and a process in which ephedrine is used with (U.S. Pat. No. 4,328,173). Similar to the optical resolution processes of the cis-permethric acid, these resolving agents are relatively expensive and the optically active transpermethric acid obtained by the resolution is not high in yield. As a result, there arises the same problem that the optically active trans-permethric acid is also expensive.